This invention is concerned with the improvements in and relating to an information recording method of recording video information on an information storage medium and an information reproducing method of reproducing the video information from the information storage medium, and more particularly to those suitable for a case where the video information recorded on the information storage medium is the digital video information compressed according to the MPEG (Moving Picture Image Coding Experts Group) standards.
In recent years, systems for playing back an optical disk on which video (or moving picture) information and audio information have been recorded have been developed. They have been widely used in the form of, for example, LDs (Laser Disks) or video CDs (Compact Disks) for the purpose of reproducing movie software or karaoke.
In this connection, the DVD (Digital Versatile Disk) standard employing the internationally standardized MPEG-2 scheme and the AC (Audio Compression)-3 or other audio compression schemes has been proposed. The DVD standard covers playback-only DVD video (or DVD-ROM (Read-Only Memory)), write-once DVD-R (Recordable), rewritable DVD-RAM (Random Access Memory) (or DVD-RW (Rewritable)).
The DVD video (DVD-ROM) standard supports MPEG-2 for moving picture compression scheme and not only liner PCM (Pulse Code Modulation) but also AC-3 audio and MPEG audio for audio recording scheme.
The DVD video standard further supports sub-picture data obtained by run-length compressing the bit map data for subtitles and reproduce control data (navigation data) for data searching by fast-forward playback or fast-rewind playback.
Furthermore, the DVD video standard supports ISO (International Organization for Standardization) 9660 and UDF (Universal Disk Format) to allow computers to read data.
For DVD video (DVD-ROM) optical disks, a 12-cm diameter single-sided single-layer disk has a storage capacity of about 4.7 GB (Giga Bytes); a 12-cm diameter single-sided double-layer disk has a storage capacity of about 9.5 GB; and a 12-cm diameter double-sided double-layer disk has a storage capacity of about 18 GB, provided that 650-nm (nanometers) wavelength laser light is used for reading.
On the other hand, for DVD-RAM (DVD-RW) optical disks, at the present time, a 12-cm diameter single-sided disk has a storage capacity of about 2.6 GB and a 12-cm diameter double-sided disk has a storage capacity of about 5.2 GB. Namely, DVD-RAM optical disks in practical use have a smaller storage capacity than DVD-ROM disks of the same size.
In playback-only DVD video (DVD-ROM), like a hierarchical file structure used by a general-purpose computer operating system, the directory structure of information (data files) recorded on an information storage medium is such that a subdirectory of video title set VTS and a subdirectory of audio title set ATS are connected to a root directory as shown in FIG. 1.
In the subdirectory of video title set VTS, various video files (including VMGI, VMGM, VTSI, VTSM, and VTS) are so arranged that the individual files can be managed in order. A specific file (for example, a specific VTS) can be accessed by specifying a path from the root directory to the file.
Specifically, the root directory of a DVD video disk includes a subdirectory called video title set VTS. The subdirectory can contain various management data files including VIDEO_TS.IFO or VTS—01—0.IFO, backup files, including VIDEO_TS.BUP and VTS—01—0.BUP, for backing up the information in those management data files, and a video data file VTS—01—1.VOB managed on the basis of the contents of the management data files and used to store digital video information. The subdirectory can also contain menu data files (including VMGM and VTSM) for storing specific menu information.
A DVD video disk is composed of a video manager VMG and at least one or up to 99 video title sets VTSs. The video manager VMG is composed of control data VMGI, VMG menu video object set VMGM_VOBS, and backup control data VMGI_BUP. Each data is recorded on an information storage medium as a single file.
As shown in FIG. 1, on the DVD video disk, the individual video title sets (e.g., video title set VTS #1 and video title set VTS #2) have to be recorded in separate files. In each video title set (e.g., video title set VTS #1), control data VTSI, VTS menu video object set VTSM_VOBS, and backup control data VTSI_BUP are recorded in separate files. Additionally, title video data VTS—01—1.VOB and VTS—01—2.VOB in the VTS are recorded in plural files.
The DVD-RAM disk uses a UDF file system, not a FAT (File Allocation Table) file system. The details of UDF will be described in details later. Like FAT, UDF enables a hierarchical structure of files and records data in files on an information storage medium. In the prior art, both of the UDF file and the FAT file are filled with data and have no unrecorded area in them.
The contents will be explained in detail using one example. For example, when a statement has been written using word processor software (such as Ichitaro, Word, or Amipro) running on a PC (Personal Computer), the written statement is recorded on an information storage medium as a file. In this case, all the file is filled with text data. Even if a space area or a continuous enter mark portion with no sentence continues long in the middle of the written sentence, that portion in the stored file will be filled with space data and enter data and therefore there will be no fully unrecorded area in the file.
Even when the user reads the document file and stores the data after deleting the middle of the sentence, an unrecorded area is never defined in the stored information and is recorded on the information storage medium as a file with the data items before and after the deleted portion putting together. As a result, the size of the file recorded on the information storage medium decreases by the amount of data in the deleted portion.
With application software running on an ordinary PC, a file read from an information storage medium for editing is transferred as it is to a buffer memory (semiconductor memory) on the PC. The edited data is stored temporarily in the buffer memory on the PC. Once the user has given an instruction to store the file, the edited data stored in the buffer memory on the PC is written over the whole file on the information storage medium. As described above, with the conventional file system, such as a FAT or UDF file system, when the file data is changed, all the data in the file is changed at a time in the overwrite process. This is different from the present invention where the data in only a part of the file is changed.
FIGS. 2A and 2B illustrate examples of reproducing video information using program chains PGCs on a DVD video disk. As shown in FIG. 2A, the playback data is divided into cells and playback sections from cell A to cell F are specified. In the individual program chains PGC #1 to #3, PGC information is defined as shown in FIG. 2B. Specifically, the table in FIG. 2B reads as follows.
1. Program chain PGC #1 shows an example of being made up of cells specifying consecutive playback sections. The playback sequence is:Cell A→Cell B→Cell C.
2. Program chain PGC #2 shows an example of being made up of cells specifying intermittent playback sections. The playback sequence is:Cell D→Cell E→Cell F.
3. Program chain PGC #3 shows an example of being made up of cells specifying disorderly playback sections, regardless of the direction of playback or repetitive playback. The playback sequence is:Cell E→Cell A→Cell D→Cell B→Cell E
By defining different program chains PGCs as described above, different display sequences can be realized for the same cells. In a DVD video disk, all the cell information is not necessarily displayed by a single program chain PGC because of the freedom of program chain PGC setting.
What has been explained above is about the data structure of the video information recorded on a playback-only DVD video disk. An information storage medium capable of recording and reproducing video information using a DVD-RAM disk or a DVD-RW disk is now being developed as one form of the DVD family.
It is desirable that the video information recording format on the information storage medium capable of video recording and reproducing should have a continuity and a relation with the data structure of a DVD video disk. In addition, a UDF file system is used for DVD-RAM disks or DVD-RW disks, as in the playback-only DVD video disk.
When the data structure of the aforementioned DVD video disk is used directly as the data structure on a recordable (videorecordable) information storage medium and the above conventional UDF (or FAT) file system is used, the following problems arise:
1. Since the control data and video data are recorded in such a manner that they are distributed over plural files, when having deleted a file by mistake, the user is unaware of the position of the error until trying to reproduce the deleted file in the course of playback. For the playback-only DVD video disk, there is no possibility that the user will delete a file. In the case of recordable/erasable information storage mediums, however, there is a danger that the user will delete a file by mistake.
2. Since the control data and video data are recorded in such a manner that they are distributed over plural files and the data structure has the same hierarchical structure as that of the computer data, it is difficult for the family user unfamiliar with the computer to understand the deleted place or the recorded place. Specifically, knowing only the VTR (Video Tape Recorder) as a medium capable of recording video information, the family user wonders which part of the single tape the place where the picture has been recorded or deleted has occupied. Therefore, showing the user small files of record or the result of erasing as they are would throw the user into confusion.
As shown in FIG. 1, in the DVD video disk, information is recorded in such a manner that it is divided into separate files by video title set VTS. Thus, when plural video title sets (VTS#1 and VTS#2 in FIG. 1) have been recorded on the information storage medium, the user familiar with only the VTR has no idea about the playback procedure.
3. With a method of allowing the family user to select a specific cell corresponding to a program chain PGC for the recorded information, some user is liable to fall into confusion. Specifically, knowing only the VTR as a medium capable of recording video information, the family user will probably wonder which part of the single tape the place where the picture has been recorded or deleted has occupied. Therefore, it would be difficult for the user to understand the concept of selecting cells by a program chain PGC on a playback-only DVD video disk.
4. In a data file recorded using the conventional UDF or FAT, there is no unrecorded area. Therefore, when part of a specific data item in a file has been deleted or a few pieces of video information have been added, the data items in front of and behind the deleted portion are squeezed together and connected or the pieces of information are added to the end of the existing data. Each time data is deleted or added, the size of the whole data file has to be changed and all the changed data file has to be recorded on the information storage medium again. As a result, it take a very long time to complete the editing process.
Specifically, with the conventional UDF or FAT, since a file has no unrecorded area, the following processes cannot be carried out:
(a) The process of changing the erased place to an unrecorded area when part of the data in a file has been deleted.
(b) The process of recording additional data on an unrecorded area in a file without changing the entire file size.
Therefore, each time the data is deleted partially or added, the file size has to be changed.
As a result, the entire file has to be recorded again on the information storage medium. In the case of a video file in which video information has been recorded, the size of a single video file is as large as more than several hundreds of megabytes (MB). If a file as large as several hundreds of megabytes is all recorded again on the information storage medium each time a slight change has been made, it will take an extremely long time to change the contents of the file.
For a further description of the prior art, reference may be made to:    Japanese Patent Application No. 040876 (filed on Feb. 23, 1998)    Japanese Patent Application No. 040877 (filed on Feb. 23, 1998)    Japanese Patent Application No. 040879 (filed on Feb. 23, 1998).